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Calculating Surfaces For Graphene Growth

The understanding of surface reconstructions has become essential as scientists seek to develop materials with tailored properties. For instance, researchers over the past few years have been searching for a process to mass-produce circuits using a material called graphene – a one-atom-thick layer of graphite – which displays unique electronic properties.

Nancy Sandler, Ph.D., an assistant professor in the Physics and Astronomy Department at Ohio University, is investigating models for surface reconstructions of silicon carbide (SiC), a substrate material used to produce graphene. Her modeling was generated with the density functional theory-based code SIESTA on the IBM Glenn Cluster at the Ohio Supercomputer Center.

“Despite the success in the fabrication of high-quality films of graphene, there is little knowledge on the mechanisms of nucleation and growth of these films on the underlying SiC material,” said Sandler. “Many of the properties of the film obtained are strongly determined by the substrate that remains after graphene separation.”

Sandler and her team studied three models, each with the addition of carbon-rich layers of different coverage and electronic properties similar to that existing before graphitization. They analyzed corresponding band structures and density-of-states, comparing them to experimental scanning tunneling microscope measurements.

The model that best described the experimental observations featured an intermediate- coverage carbon-rich layer, on top of which a complex network of three-atom products, called trimers, is formed. This trimer network produces electronic properties common to both reconstructions and provides insight into graphene formation at higher temperatures.